1. Field of the Invention
The present invention relates to multistage pressure condensers used in steam turbine plants.
2. Description of Related Art
Generally, in a steam turbine plant, steam that has driven the steam turbine is exhausted from the turbine so as to be guided to a condenser. The steam guided to the condenser exchanges heat with coolant guided to the condenser so as to be condensed into steam condensate. The steam condensate obtained in the condenser is heated via a heater and is supplied to a boiler. The heated steam condensate supplied to the boiler is turned into steam so as to be used as a driving source for the steam turbine.
In such a steam turbine plant, a multistage pressure condenser is used for achieving higher plant efficiency with increasing temperature of the steam condensate guided to the heater from the condenser, as well as for minimizing the amount of coolant used for the heat exchange performed in the condenser.
FIG. 5 schematically illustrates the configuration of, for example, a two-stage pressure condenser constituted of high-pressure and low-pressure condensers.
A low-pressure condenser 2 in a multistage pressure condenser 1 constituted of high-pressure and low-pressure condensers mainly includes a pressure bulkhead 4 that has multiple holes 8 and that partitions a low-pressure drum 3, in the longitudinal direction thereof, into upper and lower sections; a low-pressure cooling-tube bank 5 provided in the upper section of the low-pressure drum 3 and to which coolant is guided; and a reheat chamber 6 located in the lower section of the low-pressure drum 3.
Exhaust (low-pressure exhaust) guided to the upper section of the low-pressure drum 3 from a steam turbine (not shown) exchanges heat with the coolant guided to the low-pressure cooling-tube bank 5 so as to be condensed into low-pressure steam condensate. The low-pressure steam condensate is accumulated above the pressure bulkhead 4 so as to form a condensate pool 7. Since the pressure bulkhead 4 is provided with the plurality of holes 8, the low-pressure steam condensate falls toward the reheat chamber 6 from the condensate pool 7.
The reheat chamber 6 is connected to a steam duct 13 that guides the steam-turbine exhaust to the reheat chamber 6 of the low-pressure condenser 2 from the high-pressure condenser 22. Therefore, the low-pressure steam condensate falling into the reheat chamber 6 makes gas-liquid contact with high-pressure steam guided from the steam duct 13 so as to be reheated. The reheating efficiency becomes higher with increasing gas-liquid contact time between the reheated low-pressure steam condensate and the exhausted high-pressure steam.
In order to increase the gas-liquid contact time, the Publication of Japanese Patent No. 3706571 discloses providing a tray 9 for storing the low-pressure steam condensate falling into the reheat chamber 6 from the multiple holes 8 until the low-pressure steam condensate overflows therefrom, as shown in FIG. 5.
Furthermore, Japanese Unexamined Patent Application, Publication No. 2009-52867 discloses suspending an angle iron element, with its apex oriented upward, or a spiral element from the pressure bulkhead.
Moreover, Japanese Unexamined Patent Application, Publication No. Hei 11-173768 discloses suspending a cylindrical liquid film, extending in the longitudinal direction of the low-pressure drum, into the reheat chamber from the pressure bulkhead.
However, recently, there have been demands to further increase the gas-liquid contact time relative to the inventions disclosed in the Publication of Japanese Patent No. 3706571, Japanese Unexamined Patent Application, Publication No. 2009-52867, and Japanese Unexamined Patent Application, Publication No. Hei 11-173768 so as to achieve higher reheating efficiency.
In the inventions disclosed in the Publication of Japanese Patent No. 3706571, Japanese Unexamined Patent Application, Publication No. 2009-52867, and Japanese Unexamined Patent Application, Publication No. Hei 11-173768 and the case shown in FIG. 5, when the pressure difference between the high-pressure condenser 22 and the low-pressure condenser 2 increases (to, for example, 50 mmHg), the water level of the condensate pool 7 in the low-pressure condenser 2 rises, possibly causing the low-pressure cooling-tube bank 5 located above the pressure bulkhead 4 to become submerged in the condensate pool 7.
Therefore, FIG. 6 shows a measure taken to prevent the low-pressure cooling-tube bank (not shown) from being submerged in the condensate pool 7 by increasing the capacity of the condensate pool 7 by lowering a part 4a of the pressure bulkhead 4 in the low-pressure condenser 2 by, for example, about 50 cm toward the reheat chamber 6. However, if the part 4a of the pressure bulkhead 4 is lowered toward the reheat chamber 6 in this manner, the distance from the part 4a of the pressure bulkhead 4, having the multiple holes 8, to the tray 9 becomes shorter, which is a problem in that the gas-liquid contact time between the falling low-pressure steam condensate and the high-pressure steam becomes shorter, resulting in reduced reheating efficiency.
On the other hand, if the low-pressure cooling-tube bank is provided above and away from the condensate pool without lowering the aforementioned part of the pressure bulkhead toward the reheat chamber, the overall size of the condenser would increase.